1. Field of the Invention
The present invention relates to a method for producing a carbon material coated with carbon film and, more particularly, to a method for producing a carbon material preferably applied for producing carbon material or carbon composite material such as mandrels, molds, crucibles for melting metal, jigs for sealing glass, brazing jigs, graphite parts for electric furnace, and dies for continuous casting.
2. Description of the Prior Art
Hitherto, a serious problem has existed regarding the use of carbon or carbon composite materials in that carbon particles may fall off the surface of these materials resulting in pollution of the place where they are used otherwise carbon dust thereof sticks to final product resulting in reduction of productivity. In other words, dust from these materials brings about a troublesome problem, and moreover there arises another problem of environmental sanitation over the workers engaged in carbon industry. Furthermore, because the carbon or carbon composite material may react with metals to produce various carbides, application of these materials to crucibles for melting metals are obliged to be considerably restricted.
As for a method to prevent such carbon or graphite material from the mentioned falling off, it has been proposed to coat the material with pyrocarbon. This method, however, requires very complicated equipment, which is a serious disadvantage in view of industrial productivity. Moreover, in case of certain equipment such as jigs for sealing diode which need fine pores of 0.1 to 1 mm in diameter, this method shows a further disadvantage of unnecessarily filling up the fine pores with pyrocarbon.
As for materials to be used for treating molten metals keeping in contact with them, essential requirements are heat resistance, high thermal conductivity, non-affinity with molten metal, thermal shock resistance, mechanical strength, etc. Electroconductivity, oxidation resistance, impermeability, etc. should be also considered depending upon the situation.
Under such circumstances, it is a recent trend that carbon materials have been widely employed except special applications and, in particular, isotropic graphite material of which the electrical and physical properties are uniform and even is popularly adopted in many applications.
In this respect, it is noted that modern industrial facilities have increasingly required introduction of equipment of new materials under the background of recent remarkable progress in technology, new alloys under the background of diversification of needs, as well as ultra-pure metals under the background of seeking higher performance. As a result, further improvements have been also demanded as to such carbon materials for treating molten metals, in particular, those for use in continuous casting to be employed in such metal production equipments.
As another method, it has been also proposed to coat the material with glass carbon film. Also in this method, there is a disadvantage of filling up the fine pores with glass carbon film.